The present invention relates to processes and apparatuses for forming a frozen crust at the surface of a food product and to crusted products produced by such process and apparatus.
Prior to slicing food logs (e.g., turkey logs, ham logs, honey-baked ham logs, etc.) and other food products, it is known in the art to first form a frozen crust at the surface of the product. The rigid crust greatly facilitates the slicing process by providing a much firmer surface for receiving the slicer blade. Additionally, the frozen outer edge of the sliced product prevents the individual slices from folding over as they fall from the cutting machine. The slices are therefore much better suited for forming stacks and for packaging.
Turkey, ham, and other food product logs typically have square, D-shaped, or oval cross-sectional shapes and can be up to 60 inches in length or more. The sliced product produced from such logs will commonly be packaged and provided to retail outlets as, for example, 4 inchxc3x976 inch slices or 4 inchxc3x974 inch slices.
By providing a firm outer surface for receiving the slicer blade, the frozen crust greatly reduces the production of slivers or partial slices that are otherwise formed when slicing a soft log. The frozen crust therefore allows much more efficient slicing, even at greatly accelerated slicing rates. For example, a line running an uncrusted product at 400 rpm can typically be accelerated to 800, 1000, or even 1200 rpm when slicing a crusted product.
Two types of freezing processes have heretofore been used in the art. The first is a cryogenic crusting process wherein nitrogen, in either liquid or gas form, is applied to the surface of the product log for a period of from about 4 to about 12 minutes. Because of the extremely cold temperatures involved and the relatively brief period of exposure, nitrogen processes provide a highly desirable, thin product crust. The other process employed heretofore involves simply loading a large number of product logs onto a truck and placing the loaded truck in a batch freezer for 8-10 hours.
Unfortunately, each of the two prior crusting processes has significant shortcomings. The total operating cost of a nitrogen crusting process will typically be as much as about three cents or more per pound of product. In the batch freezing process, on the other hand, each truck holds about 50 logs so that, after removing the truck from the freezer, it takes approximately one hour to slice the entire batch. Thus, toward the end of the hour-long batch slicing process, the remaining product logs will be significantly or completely thawed. Additionally, such batch freezing processes are so slow that the crust formed is very thick and the temperature reduction experienced reaches all the way to the core of the product. A thick crust of this type can dull the product slicer blade very quickly.
The present invention satisfies the needs and alleviates the problems discussed hereinabove. The present invention provides a continuous freeze-crusting process which is fast but costs a great deal less than nitrogen crusting processes. The inventive process preferably utilizes ammonia, Freon, or other common refrigerants costing as little as 0.1¢ per pound of product. In addition, the inventive system continuously provides freshly crusted product to the slicer, as needed, so that no significant thawing of the crust occurs.
In one aspect, the present invention provides a process for freeze-crusting food products comprising the steps of: (a) continuously delivering the food products through a freezing apparatus and (b) exposing the food products to circulating air within the freezing apparatus at a temperature and in a manner effective for freezing an outermost layer of each food product.
In another aspect, the present invention provides a method of processing food products comprising the steps of: (a) continuously delivering the food products through a freezing apparatus; (b) exposing the food products to circulating air within the freezing apparatus having an average temperature of not greater than 0xc2x0 F. and then (c) slicing the food products. In step (b), the circulating air is circulated in the freezing apparatus in a manner effective for freezing an outermost layer of the food product in less than 30 minutes. The frozen outermost layer will preferably have a thickness in the range of from about 0.1 to about 0.5 inches.
The present invention further provides a vertical freezing unit which is particularly well-suited for use in the inventive freeze-crusting process. The inventive freezer can also be used for other types of freezing operations. The inventive vertical freezer desirably operates by cold air circulation using ammonia, Freon, or other common refrigerants. In addition, the inventive vertical freezer inverts the product (i.e., turns the product over) during the crusting or freezing process so that a much more equivalent and thorough degree of air contact occurs with all surfaces of the product. Also, because of its vertical structure, the inventive freezer has a much smaller footprint and therefore requires much less space than other types of freezers known in the art.
The inventive vertical freezing apparatus preferably comprises: a housing; a vertical conveyor positioned in the housing and having an upward path and a downward path; a refrigerating element within the housing; and circulating means for circulating air within the housing through the refrigerating element and onto products carried by the vertical conveyor.